Ethernet transport is an emerging opportunity for telecommunication carriers. The Ethernet transport network structure offers the potential to carry and deliver Ethernet connectivity with different types of services having many combinations of quality objectives, such as loss, delay and bandwidth. The Ethernet technology is undergoing a significant transformation to bring it to a level that is carrier-grade with the required management and protection functionality.
One aspect of the technology that is being enhanced is the ability to perform Operation Administration and Maintenance (OAM) functions. A key function is the ability to detect faults in the network and react in a manner to avoid impacting the customer services. To detect faults, special packets can be inserted in the data path to indicate the loss of connectivity. In the ITU-T Y.1731 standard, such packets are referred to as Continuity Check Messages (CCM) packets. The format of a CCM message is shown in FIG. 1. The packet 101 is composed of different fields including a set of flags 102. One of the flags is a Remote Defect Indication (RDI) 103 which is set to one when the path is deemed defective and a protection switching action is required. Both the upstream end 105 and the downstream end 106 of a connection-oriented path 107 send regular CCM messages to the opposite ends of the path. If one end stops receiving some number (e.g., three) of consecutive CCM messages, the path is presumed to have failed, and the other end is notified by sending a CCM messages with the RDI bit 108 set to one.
Other information can be carried in a CCM message through the use of a Type Length Value (TLV) identifier 104 which indicates that the packet includes some further information to indicate the status of other aspects of the network that require handling by the end points. For example, if a port related to a service is blocked for some reason, a port TLV indicating this “fault” condition is included in the CCM message. InterfaceStatus and PortStatus TLV's can optionally be added to a CCM. PortStatus TLV indicates the ability of the port on the node 105, 106 to pass ordinary data. InterfaceStatus TLV indicates the status of the interface of the node where the CCM message is transmitted. Both status indicators are set independently of the RDI. In most cases, the presence of one or more of these TLV's in the CCM message indicates a service-affecting issue.
If there is a local failure at one end of the path, or a condition occurs where the path can pass traffic but the CCM messages are still functioning, only the troubled end of the path will be operationally set to down, but the other end will continue to transmit traffic in the reverse direction because it needs to be notified of the problem. In this case, the InterfaceStatus TLV can be used in the CCM PDU to indicate an administrative state change, and both ends of the path will switch to the protected path.
Nodes are generally architectured with a data path 105b, 106b and a control plane 105a, 106a. The data path is responsible for processing all the traffic and ensuring that the throughput of the line rate is maintained. The control plane is responsible for managing the node and processing events at a lower speed. The current procedure for finding TLV information and reacting in an appropriate time is to have the data path parse each CCM message in case TLV information is present. The problem is that the data path needs to be extremely fast to keep up with the line rate. Parsing of the CCM messages in real time to extract the TLV information is very difficult as the TLV information is optional and can appear in any order in the message. This procedure greatly impacts scalability and leads to poor reaction time.